THE MANY MYTHS, SOME OLD, SOME NEW, OF ... - Gregory S. Paul

82 . G. S.·PAUL
Reality: As usual, life is not so simple (Figure 6; Paul, 1990a). nina and leatherbacks
are very active, fast swimmers with metabolic rates in the lower mammal range, and
very high rates of food consumption. Yet their brains are small-and simple.
Pterosaurs were highly active, insulated fliers that must have had elevated metabolic
rates, and although their brains were fairly complex, their EQ's fall entirely within
the reptile range (Figure 7). At the other extreme, some advanced rays are inactive
and bradymetabolic bottom dwellers with brains as large-as those of felids,canids,
and ungulates of similar size (Northcutt, 1977). Reef and hammerhead sharks are
bradytherms whose brains are as large as those of ground birds of similar size, and
that have enlarged, complex forebrains.
The overlap between vertebrates with differing brain sizes and physiologies is so
extensive that their traditional segregation into "lower" and "higher" vertebrates
must be considered obsolete. Brain size and complexity does not have any consistent
correlation with metabolic rates or activity levels, and cannot be used to determine
dinosaur physiology at even the gross or detailed levels. It is widely acknowledged
that small brained dinosaur species were often social and parental (Horner and
Gorman, 1988; Coombs, 1989), if sovthen they were intelligent enough to have
maintained a high level of energy consumption and production. Note that small
brains in highly energetic dinosaurs does not violate the evolutionary trend towards
increased information processing (see above). In addition to the higher rate of
generational inspired genetic turnover, the higher feeding rates of endotherms
require an order of magnitude increase in the frequency of brain activity in order to
achieve the levels of activity needed to search for and consume the food. Small
brained ants, bees and termites have also achieved a similar boost in information
processing, in their case via intense socialization.
BRADYMETABOLIC DINOSAURS COULD GROW UP FAST
Myth: It is now widely acknowledged that many or all dinosaurs grew as fast as
tachymetabolic mammals and birds, which grow 10 to 30 times faster than wild
bradymetabolic reptiles. Since many of these workers also believe that dinosaurs
combined double pump hearts with reptilian energetics, they argue that nontachymetabolic
animals can also grow rapidly (Ricqles, 1980; Regal and Gans, 1980;
Reid, 1984, 1987; Dunham et al., 1989).
Reality: This emerging myth badly needs nipping in the bud. For a free living,
self feeding juvenile to grow fast, it must have very high sustained activity levels in
order to find the abundant amounts of food needed to grow so rapidly, and the little
creature must remain warm around the clock in order to maintain continuous
growth. Both of these needs require the hyper-elevated energy levels (one third over
the mass specific adult level) seen in juvenile mammals and birds (Case, 1978). That
captive reptiles can grow much faster than their free-living counterparts only
reinforces the factthat they must have food brought to them in order to do so; they
cannot acquire enough food on their own. Excellent confirmation of the correlation
linking metabolisms and maximum potential growth rates is found in the fact that
land animals with intermediate metabolic rates, marsupials and monotremes, grow
at rates intermediate to placentals and reptiles. Note that the only fast growing
reptile, the leatherback, is a highly energetic swimmer with low locomotary energy
costs. It is hardly likely that fossil animals somehow broke these barriers. Equally
unlikely is that, if it is possible for low energy land animals to grow fast, not a